Vehicle transmissions, specifically planetary gear automatic power transmissions, typically have a park brake mechanism to resist the vehicle's natural tendency to roll down a sloped surface when the vehicle is in park. The contents of such a park brake generally include some sort of gear that is fixed with respect to the output shaft of the transmission and a pawl designed to selectively engage with the gear when the park brake is activated. The pawl substantially prevents the output shaft and attached gear from rotating when the pawl engages with the recesses between the gear teeth.
Vehicles with complex non-traditional powertrains, like electromechanical vehicles, still require a park brake mechanism. However, the alteration of some components in the transmission may require the park pawl and its complementary components to be altered as well. For example, some hybrid electromechanical transmissions require the use of two electric motors to supply power to the output shaft of the transmission.